“双低”技术应用于CTPA的可行性研究

The Application of Low Tube Voltage and Low Volume Contrast Agent Protocol in CT Pulmonary Angiography

目的:评估"双低"(低管电压与低碘量)技术在肺动脉CT血管成像(CTPA)中的图像质量、辐射剂量及临床价值。方法:前瞻性将临床疑似肺动脉栓塞(PAE)患者105例,随机分为A、B、C三组行CTPA检查(n=35)。A组:管电压120 k Vp、对比剂40m L(碘浓度350 mg I/m)、注射速率4 m L/s;B组:管电压100 k Vp、对比剂35 m L(碘浓度300 mg I/m)、注射速率3.5 m L/s;C组:管电压80 k Vp、对比剂30 m L(碘浓度270 mg I/m)、注射速率3 m L/s。三组均开启管电流调制(ATCM)技术,A组采用滤波反投影算法(FBP),B、C两组采用ASIR技术重建。记录每例患者的对比剂量、CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP),并计算有效剂量(ED)。在轴位图像测量肺动脉干、左、右肺动脉及亚段肺动脉的CT值。采用Kruskal-Wallis H检验来比较3组的辐射剂量、碘量、图像质量的主观及客观评价等指标。结果:A、B、C三组分别在肺动脉干、左、右肺动脉及亚段肺动脉的CT值差异均无统计学意义(P>0.05);三组图像背景噪声、SNR、CNR及主观评价差异亦均无统计学意义(P>0.05);与A组相比,B组和C组的ED分别降低了38.09%、51.99%;A组接受碘量分别高于B组25%和C组42.14%。结论:管电压80 k Vp、对比剂30 m L(碘浓度270 mg I/m L)、注射速率3 m L/s在肺动脉CTA中的应用是可行的,图像质量既满足诊断,又降低辐射剂量和碘量。

Objective： To evaluate the image quality, radiation dose and clinical application value of the ＂double low＂ （low tube voltage and low iodine） technology in the CT pulmonary angiography （CTPA）. Method： The patients （n = 105） with clinicaliy suspected as pulmonary embolism （PAE）, were randomly divided into group A, B and C （each n = 35）, prospectively. Group A：the tube voltage was120 kVp, and the volume of contrast agent was 40 mL （Iodine consentration： 350 mgI/mL）, flow rate 4 mL/s; Group B： the tube voltage was100 kVp, and the volume of contrast agent was 35mL （Iodine consentration： 300 mgI/mL）, flow rate 3.5 mL/s; Group C：the tube voltage was 80 kVp, and the volume of contrast agent was 30mL （Iodine consentration： 270 mgI/mL）, flow rate 3 mL/s .Group A was using filter back-projection algorithm （FBP） and both group B and C was using the technology of ASIR for reconstruction, and all groups was opening Attenuation-based online tube current modulation（ATCM） technology . Recording each patient’s CTA scan time, the volume of contrast agent, CT dose volume index （CTDIvol） and dose length product （DLP）, and calculating the effective dose （ED）, type specific dose estimation （SSDE） value and the amount of iodine.To measure the CT values of pulmonary artery trunk, left and right pulmonary arteries and subsegmental Pulmonary in the axial image .To compare the radiation dose, the amount of iodine,and the subjective and objective evaluation index of the image quality by Using Kruskal-Wallis H test. Results： The differences of the measured average CT values of the main pulmonary artery, left and right pulmonary arteries and subsegmental pulmonary artery between the three groups were not statistically significant （P 〉 0.05）; The differences of background noise, SNR, CNR and subjective evaluation between the 3 groups’ images were also not statistically significant （P 〉 0.05）. Compared with group A, the ED of group B and C were decreased by 38.09% and 51.99% respectively, and SSDE were decreased by 37.96% and 48.39% respectively. The amount of iodine in the A group was higher than that 25% in the B group and 42.14% in the C group, Conclusion： The application of the tube voltage （80 kVp）, the volume of contrast agent （30 mL） and the iodine concentration （300 mgI/mL） and flow rate 3mL/s in CT pulmonary angiography is feasible, not only can the image quality meet the Clinical Diagnosis, but also reduce the radiation dose and the amount of iodine.